In recent years, great consideration has been paid to indoor air quality (IAQ) and its influence on health of buildings occupants, especially because people spend almost 80% of their time in enclosed spaces. Ventilation systems contribute to IAQ supplying fresh air and evacuating the indoor pollutants. Air cleaning technologies are often coupled with ventilation systems for improving IAQ such as filtration for particles removal from air. Moreover, for energy saving reasons, ventilation is usually stopped or reduced during nights, weekends and/or holidays. The potential consequences of this ventilation energy optimization in relation to filtration performances and IAQ are not well-known.

In this context, a laboratory-scale air handling unit (AHU) composed of two stages of filtration has been developed to study aerosols filtration and their behaviour on filters. This lab-scale AHU is a closed-loop vent through which air can be continuously circulated for controlled temperature (T) and relative humidity (RH) set-points. The two filtration stages can be sequentially tested with prototypes filters of different efficiencies (G4 to F9 according to European standard EN779; MERV 7 to 16 according to US ASHRAE 52.2 rating) and industrial geometries (bag and pleated filters) at characteristic air filtration velocity of full scale AHU (0.1-0.9 m.s^-1; 3.9-35.4 in.s^-1). This unit was validated in terms of symmetric velocity profiles upstream first filtration stage and climatic parameters (RH and T) stability.

The validation of this unit involved the aerosols generation and the study of prototype filters performances during clogging. A PM10 aerosol was selected to clog the filters. Aerosol concentrations (upstream and downstream to each filtration stage) and filters pressure drop were measured continuously throughout the filters clogging period. Filtration efficiencies of prototype filters were observed and compared with standards. These preliminairy results have validated the use of this lab-scale AHU and the use of prototype filters for the study of filtration performances of industrial filters at controlled climatic conditions. Next steps of the project include the study of the influence of filtration cycles, which occur in full scale AHU for energy saving reasons, on IAQ regarding the aerosols.